Button cell

A button cell comprising:

• an electrode assembly comprising a first electrode, a second electrode, a separator between the first electrode and the second electrode, a first electrode tab coupled to the first electrode, and a second electrode tab coupled to the second electrode;
• a case accommodating the electrode assembly and coupled to the first electrode tab;
• a cap assembly sealing an opening in the case, the cap assembly comprising:
• a cap plate coupled to the case and covering the opening in the case;
• and
• a terminal plate coupled to the cap plate;
• and
• an insulating member having an outermost surface contacting an inner surface of the cap plate and an innermost surface facing the second electrode tab,
• wherein the terminal plate comprises:
• a flange portion coupled to and electrically insulated from the cap plate;
• and
• a tab connecting portion protruding from the flange portion toward the electrode assembly and extending through a terminal opening in the cap plate, the tab connecting portion being coupled to the second electrode tab,
• wherein outer surfaces of the flange portion and the tab connecting portion form a flat outer surface of the terminal plate, and
• wherein the tab connecting portion has a flat inner surface that protrudes into the case.